The present invention generally relates to rotary magnetic head scanning control systems in magnetic recording and reproducing apparatuses, and more particularly to a rotary magnetic head scanning control system in a magnetic recording and reproducing apparatus which comprises means for varying height positions of rotary magnetic heads so that the rotary magnetic heads accurately scan over recorded tracks during a reproducing mode, designed to control the head scanning by controlling relative height positions of respective rotary heads to become the same during a recording mode. The head scanning control system according to the present invention can positively control the scanning of the rotary magnetic heads during the recording mode, even if a format employed carries out recording and reproduction with a slow magnetic tape traveling speed and with a track pattern in which the track pitch and the track width are small.
Recently, in magnetic recording and reproducing apparatuses for home use (hereinafter simply referred to as a home VTR) having helical scanning type rotary heads, high density recording and reproduction are becoming possible due to improvements in the magnetic tape and the realization of high density rotary heads. Accordingly, home VTRs have been manufactured which are capable of carrying out recording and reproduction of durations longer than those of conventional VTRs, by reducing the tape traveling speed, the track pitch, and the like. However, because a tape driving system in the home VTR has a simplified construction in order to reduce the cost of the apparatus, it becomes difficult to accurately and stably maintain a desired tracking accuracy by scanning over bends in video tracks, during the high density recording and reproduction. Especially during a so-called interchanged reproduction in which a magnetic tape recorded by one home VTR is reproduced by another home VTR, it becomes difficult to stably maintain the above desired tracking accuracy, and a high quality picture cannot be obtained.
Hence, as a method of solve the problems with respect to the tracking introduced during the high density recording and reproduction, and eliminate noise bar introduced during a special reproduction mode such as a slow-motion reproduction mode, still reproduction mode, and quick-motion reproduction mode in which reproduction is carried out with a tape traveling speed which is different from the tape traveling speed upon recording, that is, to eliminate the noise bar introduced because the rotary heads do not accurately scan over the recorded tracks in the conventional VTR, a head moving mechanism is provided in the home VTRs which are recently being reduced to practice. The head moving mechanism displaces the rotary heads in a direction perpendicular to a rotating plane of the rotary heads, and displaces the rotary heads in a direction perpendicular to the track longitudinal direction, that is, along the width direction of the track.
According to a tracking control system employing the above described head moving mechanism, tracking control is carried out so that the rotary heads accurately scan over the recorded tracks, and as a result, a fine reproduction can be carried out. However, at a terminating point of the reproduction accompanying the above tracking control, the relative height positions of the plurality of rotary heads are not necessarily the same. In addition, if a piezo-ceramic material and the like, for example, is used for the head moving mechanism, the rotary heads do not return perfectly to their neutral positions even when application of a control voltage is stopped at the terminating point of the reproducing mode, because the piezo-ceramic material generally accompanies hysteresis. As a result, the relative height positions of each of the rotary heads do not become the same.
If each of the rotary heads are not at the same height position during the recording mode, side edges of formed tracks may overlap. Moreover, gaps may be formed between tracks, and form an unrecorded bands. Hence, as will be described hereinafter in conjunction with the drawings, the conventional apparatus recorded a pilot signal for head scan control during a predetermined interval during the recording mode, and set the mode to the reproducing mode during a succeeding predetermined interval. A crosstalk component of the pilot signal previously recorded on the adjacent track is reproduced during this reproducing mode during the succeeding predetermined interval. A control signal is obtained from this reproduced crosstalk component, and the height position of one head was controlled to become the same as the height position of another head by use of the control signal.
However, if the magnetic tape traveling speed and the track pitch are reduced to downsize the VTR and carry out recording with respect to the magnetic tape with a higher density, the so-called H-shift (shift in horizontal scanning periods) among adjacent tracks becomes small as will be described hereinafter. Thus, even if the mode is temporarily set to the reproducing mode during the recording mode to reproduce the pilot signal recorded on the adjacent track as crosstalk, the reproducing period is too short to positively reproduce the pilot signal. Therefore, there was a disadvantage in that a positive head scan control could not be carried out.